Hard-disk drives, and other magnetic media, are the storage media of choice for computers and related devices. They are found in most desktop and laptop computers, mobile communication devices, media recorders and players, and instruments for collecting and recording data. Hard-disk drives and other magnetic media are also deployed in arrays for network storage.
Magnetic media store information magnetically. The disk in a hard-disk drive, for example, is configured with magnetic domains that are separately addressable by a magnetic head. The magnetic head moves into proximity with a magnetic domain and alters the magnetic properties of the domain to record information. To read the recorded information, the magnetic head moves into proximity with the domain and detects the magnetic properties of the domain. The magnetic properties of the domain are generally interpreted as corresponding to one of two possible states, the “0” state and the “1” state. In this way, digital information may be recorded on the magnetic medium and read thereafter.
In a magnetic memory device, a magnetically active cell is set to a desired property by exposure to electric current from one or more circuit elements positioned proximate the cell. The cell is typically separated from a magnetically inactive element by a tunnel barrier, and the resistance of electric flow through the cell depends on its state of magnetization. Thus, the state of the cell can be determined by measuring the resistance of electric flow through the cell.
The magnetic medium in a hard-disk drive is generally a glass, composite glass/ceramic, or metal substrate, which is generally non-magnetic, with a magnetically susceptible material deposited thereon. The magnetically susceptible layer is generally deposited to form a pattern, such that the surface of the disk has areas of magnetic susceptibility interspersed with areas of magnetic inactivity. The non-magnetic substrate is usually topographically patterned, and the magnetically susceptible material deposited by spin-coating or electroplating. The disk may then be polished or planarized to expose the non-magnetic boundaries around the magnetic domains. In some cases, the magnetic material is deposited in a patterned way to form magnetic grains or dots separated by a non-magnetic area. In an MRAM device, the magnetically active cells are typically deposited on an insulator, such as glass.
Conventional approaches to creating discrete magnetic and non-magnetic areas on a medium have focused on forming single bit magnetic domains that are completely separate from each other, either by depositing the magnetic domains as separate islands or by removing material from a continuous magnetic film to physically separate the magnetic domains. A substrate may be masked and patterned, and a magnetic material deposited over exposed portions, or the magnetic material may be deposited before masking and patterning, and then etched away in exposed portions. The size of addressable cells that can be formed using such methods is currently limited by the field separation achievable using deposition and/or etching methods. Thus, there is a continuing need for methods of forming substrates having a pattern of magnetic properties resolvable over increasingly small domains.